Calcium and cholecalciferol: effects of small supplements in normal men

The effect of small calcium and vitamin D supplements on mineral metabolism in normal persons is unclear. To investigate the biochemical response to these medications, we administered 1000 mg Ca and 25 micrograms cholecalciferol per day or a placebo to 92 normal men for 1 y. The Ca and cholecalciferol were tolerated well. 25-Hydroxycholecalciferol [25-(OH)D] and 24,25-dihydroxycholecalciferol [24,25-(OH)2D] levels rose in treated subjects; there was no definite change in 1,25-(OH)2D concentrations. The average difference in 25-(OH)D levels between treated and untreated subjects was 30 nmol/L at 1 y. Fasting serum Ca, alkaline phosphatase, creatinine, and parathyroid hormone levels and the fasting urinary excretion of Ca, phosphorus and cAMP, were not affected. However, 24-h urinary Ca excretion was higher in the supplemented group (3.5 +/- 1.9 vs 4.7 +/- 1.7 mmol/d, p = 0.006). Serum P concentrations were slightly higher in the supplemented group at 1 y. In normal men small calcium and cholecalciferol supplements are safe, provide adequate vitamin D nutrition and apparently increase net gastrointestinal Ca absorption.